There has been proposed a related-art liquid reservoir including a liquid level detection sensor used for detection of a height position of a liquid level of a liquid accumulated in the liquid reservoir (see, for example, Patent Literature 1). The liquid reservoir and a liquid level detection mechanism described in Patent Literature 1 include a container configured to store a liquid and a gas therein, a supporting member having an upper end portion connected and fixed to an upper surface portion of the container, a heating resistor mounted to a lower end portion of the supporting member, and a voltmeter configured to detect a voltage applied across both ends of the heating resistor.
A voltage value detected by the voltmeter when the heating resistor is immersed into a liquid surface in the container and a voltage value detected by the voltmeter when the heating resistor is not immersed into the liquid surface and is in contact with the gas differ from each other. Therefore, with the technology described in Patent Literature 1, the liquid level is detected based on the voltage value that differs depending on whether or not the heating resistor (heat generating element) is immersed into the liquid surface.